Search

In the context of the subsurface pollutant detection using cooperative targets probed by ground penetrating RADAR (GPR), we assess the sampling frequency stability of the instrument as needed to make sure any time delay variation between echoes is associated with subsurface chemical detection and not with instrument drift. Thanks to surface acoustic wave (SAW) transducers designed as GPR cooperative targets, the sampling frequency of the sensors and Software SPIDAR GPR control unit is characterized for short- and long-term sampling rate stabilities. The long-term stability of the instrument is below the phase measurement noise of the SAW cooperative target. However, short-term (within each trace) phase fluctuations are observed, hinting at short-term stroboscopic delay synthesis artifacts. Having demonstrated the stability of the baseline, we demonstrate gas-phase pollutant detection in the subsurface environment using GPR interrogation of a SAW sensor functionalized with a dedicated coating for reacting with hydrogen sulfide. Finally, for onsite long-term monitoring, an embedded vector network analyzer is shown to exhibit sufficient stability and the targeted performance for this measurement by recovering the time-domain response through the inverse Fourier transform of the frequency swept characterization of the sensor. [ABSTRACT FROM AUTHOR]

Abstract: Among specific sensitive materials synthesized for chemical sensor development, cobalt corrole have shown attractive capabilities for CO detection . In this paper, we investigate the possibility to exploit such materials to develop surface acoustic wave (SAW)-based sensors. We actually demonstrate that SAW devices using delay line configuration allow investigating the molecular recognition occurring in non-conductive sensing layers of cobalt corroles. We have monitored phase variations of SAW devices versus various CO concentrations. Moreover, a specific testing setup has been developed to precisely dose CO at low concentrations, to avoid any CO leakage in the environment, to systematically control environmental parameters and to allow regeneration of the trapping sites of CO. [Copyright &y& Elsevier]

Single-mode waveguides were fabricated by deep ultraviolet radiation in poly(methyl methacrylate) (PMMA). Using a masking process, the radiation modifies the refractive index of the PMMA forming core and cladding regions for waveguiding. Following the fabrication of the waveguides, the small molecule material aluminum tris(8-hydroxyquinoline) doped with the laser dye DCM is deposited directly onto the waveguide structures. By optical pumping (lambda=355 nm) amplified spontaneous emission was observed at the end facets of the waveguides [ABSTRACT FROM PUBLISHER]

Surface acoustic wave (SAW) transducers propagating shear waves are compatible with sensing chemical compounds in a liquid phase. However, if the liquid surrounding the sensor possesses a higher permittivity than the piezoelectric substrate, then the interdigitated electrodes for converting the incoming electromagnetic wave to acoustic waves are susceptible to capacitive short-circuiting, leading to excessive insertion losses. By using high-permittivity lithium tantalate oxide (LTO), we demonstrate chemical sensing in water without the need for dedicated microfluidic packaging. Nevertheless, the gravimetric sensitivity of these package-less transmission Love-mode delay lines remains comparable to that of low-permittivity quartz when appropriately tuning the guiding layer of thin film to confine energy to the surface in a Love mode. We extend the transmission line gravimetric sensitivity measurement to a reflective delay line geometry for passive transducers that can be wirelessly probed. For instance, ground-penetrating radar (GPR) can be used for subsurface sensing, here targeting water pollution detection, operating in the 100-500-MHz range. This center frequency was selected as a tradeoff between penetration depth (lower frequency) and antenna size (smaller at higher frequency). Nonspecific binding of proteins detection is shown in the context of biosensing applications.

The detection of organophosphates, a wide class of pesticides, in water-solution has a huge impact in environmental monitoring. Acoustic transducers are used to design passive wireless sensors for the direct detection of pesticides in water-solution by using tailored polymers as sensitive layers. We demonstrate by combining analytical chemistry tools that organophosphate molecules strongly alter polymer layers widely used in acoustic sensors in the presence of water. This chemical degradation can limit the use of these polymers in detection of organophosphates in water-solution.

Long-term monitoring of organic pollutants in the soil is a major environmental challenge. We propose to meet this issue by the development of a polymer dedicated to selectively react with H 2 S, coating surface acoustic wave transducers designed as passive cooperative targets with the compound, and probing their response using Ground Penetrating RADAR, thus providing the capability to monitor the presence of H 2 S in the subsurface environment. The selectivity is brought by including lead(II) cation in a reticulated polymer matrix which can be deposited as a thin layer on a surface acoustic wave sensor. We demonstrate a signal enhancement mechanism in which water absorption magnifies the signal detection, making the sensor most sensitive to H 2 S in an underground environment saturated with moisture.

The fast and efficient detection of foodborne pathogens is a societal priority, given the large number of food-poisoning outbreaks, and a scientific and technological challenge, given the need to detect as little as 1 viable cell in 25 gr of food. Here, we present the first approach that achieves the above goal, thanks to the use of a micro/nano-technology and the detection capability of acoustic wave sensors. Starting from 1 Salmonella cell in 25 ml of milk, we employ immuno-magnetic beads to capture cells after only 3 h of pre-enrichment and subsequently demonstrate efficient DNA amplification using the Loop Mediated Isothermal Amplification method (LAMP) and acoustic detection in an integrated platform, within an additional ½ h. The demonstrated 4 h sample-to-analysis time comes as a huge improvement to the current need of few days to obtain the same result. In addition, the work presents the first reported Lab-on-Chip platform that comprises an acoustic device as the sensing element, exhibiting impressive analytical features, namely, an acoustic limit of detection of 2 cells/μl or 3 aM of the DNA target and ability to detect in a label-free manner dsDNA amplicons in impure samples. The use of food samples together with the incorporation of the necessary pre-enrichment step and ability for multiple analysis with an internal control, make the proposed methodology highly relevant to real-world applications. Moreover, the work suggests that acoustic wave devices can be used as an attractive alternative to electrochemical sensors in integrated platforms for applications in food safety and the point-of-care diagnostics., (Copyright © 2018. Published by Elsevier B.V.)